Induced and suction draft device



@cit. 1923. 1,47%187 G. J. PRAT INDUCED AND SUCTION DRAFT DEVICE FiledJune 4, 1920 use ' formed into suction draft-that is to sage of beraised vertically by GEORGES JULES FEAT, 0F PARIS, FRAN'CE.

INDUCED AND $UCTION DRAFT IDEVECE.

Application filed June 4-,

To aZZ whom it may concern:

Be it known that I, Gnonons Juries citizen of the Republic of France, reat Pa is, France, M6 Avenue des Champs Elysees. have invented certainnew and useful Improvements in Induced and Sue tion Draft Devices, ofwhich the following is a specification.

The object of the invention is to enable induced draft-that is to saydraft in which the fan draws only a portion. of the flue gases and blowsit into the chimney, said portion carrying along the remainder of theflue gases by ejector actionto be transsay draft in which the whole ofthe flue gases are passed through the fan. This is effected by providingan auxiliary fan adapted to cooperate with the main fan. in such amanner that either fan is capable of operating alone for induced draft,but that the two fans will worksimultaneously for suction draft, amovable means being provided to shut off in the latter case the directpasgases etween the chimney foot and its upper portion except by way ofthe fans.

The accompanying drawing illustrates diagrammatically a partial verticalsection of a chimney provided with an arrangement in accordance with theinvention, one of the fans being shown in vertical section.

At the foot of the chimney a which is of suitable bi conical form, arearranged two centrifugal fans (Z, 9 whose inlets g) 79 respectively, areopen to the lower chimney portion so as to receive the combustion gases,and their blades 9 open into the sta tionary discharge chamber such as7" which terminates in a delivery pipe 0 for fan d, and f for g. Saidpipes c f terminate in blowing nozzles 5 6 respectively, which open intothe chimney, the nozzles Z) c are preferably concentrically arranged,one inside the other. A movable shut-oil device or damper 5 surroundsthe outer nozzle e, and is adapted to means of chain 2' passing overpulleys j and operable by a Windlass all these parts are showndiagrammatically and may be replaced by any other known means for andlowering the damper The fans a? g are each mounted on a shaft such as sand each fan or k is lowered around the N20. Serial No. 386,583.

is individually driven by a suitable source of power, for instanceelectro motor 1* in working with induced draft, the dampnozzle 6 in theposition shown in full lines. One of the fans (Z or g is alone operated,and draws in a portion only of the flue gases through its inlet 39 or pand forces it through its discharge pipe 0 (or f) and nozzle h (or 6)back into the upper part of the chimney a. Said portion of gases issuingfrom Z; (or 6) draws by induction the remainder of the flue gases thatascend directly up the chimney as shown by arrow F and around thenozzles b, e.

For direct I lifted to the position indicated by dotted lines untilitcloses the space between the nozzle 6 and the wall of chimney a.Thereafter no gases can pass directly up the chimney, but the two fans(Z, 9 will draw the whcleof the flue gases through their inlets p p andforce thorn jointl tnough their r spective discharge pipes c, f andnozzles 6, e.

The purpose of this method of operation is the following: Whencentrifugal fans are driven at substantially constant speed, as forinstance when they are driven by an asynchronous electric motor, it iswell known in the art that their efiiciency is high only for a givenvolume of gases delivered with the so-called equivalent orifice. If onefan alone were working, its efficiency, if good when it delivers thegases for induced draft, would not be satisfactory when the laroervolume of ases is to be delivered for suction draft of suitable capacityto der of the gases which the first fan cannot ehiciently carry, theeili iency of hot; fans is maintained satisfactory.

-W hat I claim is:

-1. In an induced draft device for chimneys or the like, a fan adaptedto work alone to draw only a portion. of the gases from the foot'of thechimney, a nozzle blow' said portion of gases up the chimney to carryalong the remainder of gases, a second fan adapted to draw gases fromthe foot of the chimney and provided also with a blowing nozzle, andmeans for shutting oil the dideliver the remainre t passage of gases upthe chimney suction draft the dam er IL is By causing a second fanwhereby the two fans are caused to' draw together the whole of thechimney gases.

2. In an induced draft device, a plurality offan's each adapted to drawa'portion of the gases from the foot of the chimney, said fans havingconcentric blowing nozzles, and means for causing the fans to drawtogether the whole of the chimney gases.

3. In an induced draft device, a fan adapted to work singly to draw aportion of the gases from the-foot of the chimney, a nozzle on the]discharge end of said fan blowing said portion of gases up the chimneyto draw the remainder of gases, a second fan adapted to draw gases fromthe foot of the chimney and provided also with a blowing nozzleconcentric with the former nozzle and a damper adapted to shut oil thepassage of gases in the chimney around the nozzles.

4. In an induced draft device, a bi-conical chimney, two fans eachadapted to draw from and return to the same chimney a portion of thegases therein when either tan works alone, said fans having concentricblowing nozzles and a damper adapted to shut off the passage of gasesbetween the nozzles and the chimney whereby the fans are caused to drawtogether the whole of the gases.

In testimony whereof I ailix m signature.

GEORGES JULES PRAT.

